Predicted alterations in tertiary structure of the N-terminus of Na+/K+-ATPase [alpha]-subunit caused by phosphorylation or acidic replacement of the PKC phosphorylation site Ser-23

• Published in: Cell biochemistry and biophysics 2002-01, Vol.37 (2), p.83
• Main Authors: Brandt, Wolfgang, Anders, Alexander, Vasilets, Larisa A
• Format: Article
• Language: English
• Subjects: Kinases; Proteins
• ISSN: 1085-9195; 1559-0283
• DOI: 10.1385/CBB:37:2:083

The protein kinase C (PKC)-mediated phosphorylation of the Na^sup +^/K^sup +^-ATPase α-subunit has been shown to play an important role in regulation of the Na^sup +^/K^sup +^-ATPase activity. In the rat α^sub 1^-subunit, phosphorylation occurs at Ser-23 and results in inhibition of the transport function of the Na^sup +^/K^sup +^-ATPase, which is mimicked by replacing the Ser-23 by the negatively charged glutamic acid or by aspartic acid. Using comparative molecular modeling, we investigated whether phosphorylation or acidic replacement at position 23 causes a dramatic change in the molecular electrostatic potential at position 23 as a result of insertion of a negative charge of the phosphoryl group or Glu per se, or whether, alternatively, the modification causes larger-scale conformational changes in the N-terminus of the α-subunit. The results predict a considerable conformational change of the 30-residue stretch around Ser-23 when mutated to the residues carrying a net negative charge or being phosphorylated. The structural rearrangements occur within the N-terminal helix-loop-helix motif with a set of charged residues. This motif has structural homology with one in the Ca^sup 2+^-ATPase and may form a function-related structural site in the P-type ATPases. Comparative molecular modeling indicates a lengthening of the interhelical loop and an order-to-disorder transition by disrupting a helix at position 23 because of posphorylation.[PUBLICATION ABSTRACT]